Explanation:

- The velocity of winds is mainly controlled by multiple factors.

- Option 1: Pressure gradient

- When there's a difference in air pressure between two locations, air (wind) naturally moves from high to low pressure.

- Option 2: Pressure gradient and humidity

- Humidity doesn't directly affect wind speed; it impacts air density and weather, not the velocity of wind itself.

- Option 3: Coriolis effect

- The Coriolis effect, due to Earth's rotation, changes wind direction, not the speed.

- Option 4: Pressure and earth’s rotation

- The main factors determining wind velocity are the pressure gradient (for speed) and Earth’s rotation via the Coriolis effect (for the resulting speed and direction).

Correct answer: Option 4